Toggle arm clamp for lift trucks

ABSTRACT

A lift truck clamp for paper rolls, or similar objects, having one swinging arm to increase the range of diameters which can be handled. A toggle linkage is used to control the movement of the swinging arm. The pivot point is so placed as to allow a much shorter swinging arm.

nited States Patent Inventor Stuart W. Sinclair Houston, Tex.

Appl. No. 835,660

Filed June 23, 1969 Patented Sept.- 14, 1971 Assignee Anderson, Clayton& Co. Houston, Tex.

TOGGLE ARM CLAMP FOR LIFT TRUCKS 5 Claims, 5 Drawing Figs.

US. Cl 294/88, 214/653, 294/104 Int. Cl 1366f 9/18 Field of Search214/653; 294/104, 88

[56] References Cited UNITED STATES PATENTS 3,449,009 6/ 1969 Faust294/104 Primary Examiner-Gerald M. Forlenza Assistant Examiner-George F.Abraham Att0rneysJames F. Weiler, Jefferson D. Gillcr, William A.

Stout, Paul L. De Verter, ll, Dudley R. Dobie, Jr. and Henry W. HopeABSTRACT: A lift truck clamp for paper rolls, or similar objects, havingone swinging arm to increase the range of diameters which can behandled. A toggle linkage is used to control the movement of theswinging arm. The pivot point is so placed as to allow a much shorterswinging arm.

PATENTEI] SEP 1 4 i971 SHEET 3 OF 3 TOGGLE ARM CLAMP FOR LIFT TRUCKSBACKGROUND OF THE INVENTION The present invention relates to a clamp forlift trucks and the like, and more particularly to a clamp having aswinging arm, particularly suited for use with and manipulation ofcylindrical loads, such as rolls of paper, in a variety of diameters.

Clamping mechanisms of the general type are illustrated in the patentsto Farmer, U.S. Pat. No. 2,874,862, Faust, U.S. Pat. No. 3,127,209 andBjorklund, U.S. Pat. No. 3,180,672. These prior structures all utilize aclamp having one pivoted arm, which arm pivots only after the twoload-engaging arms have moved to a predetermined spacing. Thus, theprior devices utilize arms which move in a parallel fashion forapproximately one-half of their scope, and then the pivoted arm beginsto pivot so as to pick up small paper rolls, with an immediate decreasein mechanical advantage from the moment of pivoting onward.

In clamp designs for picking up paper rolls, the length of the short armis determined when a roll of maximum diameter is lying on its axis onthe floor and butts against the front plate of the clamp. The long armlength must be such as to reach across a diameter, drawn from thetangent of the short arm through the center of the roll. In mostinstances, the long arm can be a little shorter, and in this case, themanufacturer depends upon friction to keep the roll from squirting out.With the foregoing information, the parameters for maximum rolls areestablished. However, for small rolls the problem is to reach across theroll and still pick it up off the floor. The sort arm must, of course,stay next to the floor. Consequently, the long arm has to travel theentire distance across the clamp, which is the difference in diametersbetween the maximum roll and the smallest roll. For a variety ofmechanical reasons, pivoting long arms are used so that a wider range ofrolls can be handled. The pivoting mechanism itself must also clear boththe large and small rolls.

On the other hand, when breaking paper rolls out of railroad cars ortrucks, the rolls are generally set on end. Consequently, the long armmust not be too much longer than the short arm, or it is impossible tomaneuver into the railroad car and to break fashion, one roll from otherclosely spaced rolls. F urther if the long arm is too long, it willcause paper damage or require too much space to encircle the roll or itmay not be able to grip the roll at all because of maneuvering problems.

Finally, the theoretical pressure required to lift, and otherwise handlea paper roll, rises in a smooth curve dependent upon the roll diameter.With the usual pivoting arm, the pressure supplied by the clamp is atits maximum when the two arms are moving in a parallel fashion, butdrops sharply when the cam-operated pivot engages. That is to say, theforce supplied by these devices is not proportional to the weight of therolls handled. These deficiencies are solved with the present invention.

SUMMARY In general, the present invention provides a clamp having ashort and a long swinging arm, wherein the swinging arm is continuouslyand positively actuated by a toggle linkage so that the force suppliedby the clamp is substantially proportional to the weight of the rollbeing handled. Further, the pivot point of the swinging arm is locatedcloser to the short arm, resulting in substantially reducing therequired length of the swinging arm.

By the use of the toggle linkage mechanism of the present invention, theswinging arm moves substantially parallel to the short arm for the firstportion of the clamping action, then begins to pivot at an increasingrate. However, the force supplied by the toggle mechanism results in acurve which is substantially proportional to the weight of whateverdiameter roll of paper is being handled. Thus, the present inventioneliminates a sudden change in mechanical advantage which on occasionwith prior devices, has resulted in an inability to handle certainintermediate size rolls.

Further, the present invention allows pivot point of the swinging arm tobe located closer to the short arm and to the front plate of the clamp.This location of the pivot point allows a substantial reduction in therequired length of the swinging arm with several attendant advantages.First, it makes possible the use of a swinging arm which is no longerthan the long arm in a nonpivoting type clamp of the long and short armvariety. This results in a much more maneuverable clamp, with itsability to break out rolls of paper with minimum clearances. Further,since the pivot point of the swinging arm is located closer to the shortarm, the pads at the ends of the arms need not be pivotal through thelarge angular range heretofore required.

Advantageously, the present invention, through the use of the togglelinkage, provides a swinging arm which is positively actuated, and doesnot depend upon cams, springs or torsion bars for determining theposition of the swinging arm at any given moment.

Thus, it is an object of the present invention to provide a swinging armclamp wherein the pressure applied to the load by the clamp wherein thepressure applied to the load by the clamp varies in proportion to thediameter of the roll being handled, as well as to provide a swinging armclamp wherein the length of the swinging arm is substantially reducedover the length of pivoting arm clamps heretofore utilized.

Other and further objects, features and advantages will be apparent fromthe following description of the presently preferred embodiment of theinvention, given for the purpose of disclosure when taken intoconjunction with the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Like character references designatelike parts throughout the several views of the drawings, which are:

FIG. I is a graph diagrammatically illustrating the relationship betweenapplied force and roll diameter,

FIG. 2 is a side view of the present invention shown attached to apartially illustrated lift truck,

FIG. 3 is a top view, with partial sections, taken along the lines 3-3and 3'3' of FIG. 2,

FIG. 4 is a view similar to FIG. 2, showing the clamp of the presentinvention in position for maximum roll diameters in full lines, and forminimum roll diameters in broken lines, and

FIG. 5 is partial perspective view of the toggle linkage assembly seenin FIGS. 2 and 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,and particularly FIG. 1, a plot of force versus roll diameter isdiagrammatically illustrated. It is to be noted that between the limitsof a minimum and maximum roll diameter, the theoretical pressurerequired to clamp and lift a paper roll gradually increases in a smoothcurve from a low force level to a higher force level. Thistheoretical-pressure required is, of course dependent upon a number offactors, including the length of the roll, as well as the coefficient offriction, and consequently is given only diagrammatically. Alsodiagrammatically illustrated is the pressure curve which results fromthe use of the ordinary pivoting arm paper roll clamp, such as isillustrated in the three patents previously mentioned. Note that while alarge force is available for maximum roll diameters, the force availabledrops instantaneously to a much lower level upon the engagement of thecam to begin the pivoting arm movement shown by the prior art. Noticealso that the maximum pressures and the point of cam engagement arecritical if the prior art devices are to avoid the area illustrated at10 on the chart. This area 10 shows that the available pressure is lessthan the theoretical pressure required, and consequently, the usualpivoting device is unable to effectively handle a roll in thisintermediate diameter range between points 11 and 12.

On the other hand, the available pressure from the toggle armarrangement of the present invention is represented by the curve labeledtoggle arm pressure. NOte that this available pressure is always abovethe theoretical pressure required, and that the toggle arm pressuresubstantially tracks the theoretical pressure required over the entirecurve. Said another way, the toggle arm pressure available from thepresent invention varies continuously in proportion to the diameter ofthe roll being handled.

Referring now to FIG. 2, a lift truck 14 is diagrammaticallyillustrated, having mounted thereon a conventional carriage 16 which mayinclude rotating, tilting, elevating and side shifting functions.Suitably attached to the carriage 16 by the frame 20 is the toggle armclamp 18 of the present invention. Extending from the frame are thelower or short arm 22 and the swinging arm 24. Pivotally attached to theends of both the short and swinging arms, as by hinges 25, are loadengaging pads 26 which are curved to generally mate with the peripheryof the maximum diameter roll to be handled. Pivotally attached to theinner edges of the pads 26 are pad limiting links 28 which function toprevent the pads 26 from pivoting beyond a predetermined point withrespect to the arms 22 and 24 when the pads are tip loaded. Referringbriefly to FIG. 5, it is noted that the pad limiting links 28 extendfrom a pivotal connection with the pad 26 through an opening 30 withinthe arm 24, and as is seen in FIG. 3, the extension ends in a T-head 32on the link 28. By this simple expedient, the load engaging pads 26 arelimited in their pivotal movement.

Referring again to FIG. 2, it is to be noted that the short arm 22 isattached to a mounting bracket 34 whose extension forms a slide 36 whichextends within the frame 20 of the clamp 18. The slide 36 moreparticularly slides within a guide 38 which forms a part of the frame20, best seen in FIG. 3.

The swinging arm 24 is pivotally attached to the upper mounting bracket40 by the pivot 41 which is barely discernible in FIG. 2 because it iscovered by pivot 66 to be hereinafter described. I-Iowever, pivot 41 isseen in section 33' of FIG. 3 and in broken lines in FIG. 4. Forming apart of the upper mounting bracket 40 are slides 42 which slide withinguides 44 in the upper part of the frame 20. Referring now to FIG. 3, atop view of the bracket 40, slides 42 and guides 44 are seen.

As seen in FIG. 3, the particular embodiment illustrated herein utilizesguides 44 on either side of the frame 20 for the upper slides 42, aswell as a pair of guides 38 for the lower arm slides 36. The guides haveslots on the front to allow the brackets entry to the slides, as seen at43. Mounted vertically along the frame 20 is a hydraulic motor 46, oneend of which is attached to the frame 20 and the other end attached tothe slide or bracket 34. In a similar manner, a second hydraulic motor48 is attached to the frame 20 and to the upper bracket 40. Uponactuation of hydraulic motor 48, in a conventional manner, the slides42, and thus the mount 40, may be made to move upwardly and downwardlyin the guide 44 and thus the frame 20. By the same token, upon actuationof the motor 46, the slides 36 and thus the mount 34 and lower arm 22may be moved upwardly and downwardly in the guides 38 and thus the frame20.

Illustrated generally as 50 and best seen in FIG. 5, is the togglelinkage which interconnects the frame 20, bracket 40 and the swingingarm 24. The function of the toggle linkage 50 is to control all of themovement of the swinging arm 24 as the hydraulic motor 48 pulls themount 40 toward the short arm 22, so as to grasp a load therebetween.

Extending from and mounted on the upper bracket 40 is the heel 52.Pivotally attached to the inward lower end of the heel 52, as by pivot41, is the swinging arm 24. Notice that the pivot 41 is adjacent thefront of the frame 20. By comparing FIGS. 4 and 5, it is thus seen thatactuation of the motor 48 results in reciprocation of slide 42 and thusthe frame 40 and heel 50, which moves the pivot 41 and inward end of theswinging arm 24 along the frame 20 toward and away from the short arm22. The remainder of the toggle linkage 50 is utilized through pivot 54to control the angularity and displacement of the swinging arm 24 withregard to the frame 20. The pivot 54 pivotally interconnects the outerupper portion of swinging arm 24 and link 56, which is best seen inbroken lines in FIGS. 4 and in full lines in FIG. 3.

Pivotally attached to the heel 52 is the rocker crank 58 by pivot 60.Also pivotally connected to the rocker crank 58 is the link 56 at pivot62, seen in FIG. 4. Finally, the rocking lever 64, seen in FIGS. 4 and 5is also pivotally connccted to the rocker crank 58 at pivot 66, whilethe opposite end of rocking lever 64 is pivotally connected to the frame20 at pivot 68. Notice that pivot 66 is substantially coincident withpivot 41 when the swinging arm 24 is widest open, and remains so forapproximately one-third of the travel of the bracket 40. I

In operation, it is thus seen that as the motor 48 is actuated andassuming that the swinging arm 24 is in its upward position, the uppermount 40 is pulled downwardly and is guided by the slides 42 in theguides 44. Since the heel 52 is attached to the upper mount 40, itsimilarly moves downwardly, along the front of the frame 20. This actionalso moves the pivot 41 and therefore the innermost portion of the arm24 along the frame 20. At the same time, the rocking lever 64 beingpivoted to the frame 20 at pivot 68 causes the rocking crank 58 to pivotabout the pivot 60 resulting in pushing the link 56 about the pivot 62as well as about the pivot 54, causing the upper part of the swingingarm 24 to move outwardly with respect to the frame 20, thus swinging theswinging arm 24 about the pivot 41 and toward the short arm 22.

Notice particularly that the pivot 66 is substantially coincident withthe main pivot 41 of the swinging arm 24. So long as these two pivotsremain in substantial coincidence, the swinging arm 24 remainssubstantially perpendicular to the frame 20. It is only when the pivots66 and 41 move out .of coincidence that the rocker crank 58 begins tocause the swinging arm 24 to pivot about the pivot 41. This does notoccur until after approximately one-third of the total downward movementof the bracket 40 or heel 52. Then, as the two pivots move out ofcoincidence, the swinging arm begins to pivot about the pivot 41 towardthe short arm 22, while at the same time the pivot 41 is moveddownwardly as the mount 40 and heel 52 move downwardly. As can be seenby referring again to FIG. 1, so long as the pivots 66 and 41 are insubstantial coincidence, the full force of the hydraulic motor 48 isavailable to act upon the load being handled. However, as the two pivotsgo out of coincidence, the mechanical advantage begins to vary inproportion to the diameter of the load to be handled. Thus, the presentinvention provides pressure between the clamping arms in proportion tothe pressure actually required to handle the load involved.

As shown in FIG. 4, the short arm 22 moves upwardly upon actuation ofthe hydraulic motor 46 which moves the slide 36, mount 34 and thus theshort arm 22, all as shown in broken lines. This feature allows rolls ofeven smaller diameter to be handled by the present clamp.

As was previously mentioned, the carriage 16 may include suchconventional functions to allow rotating the clamp 18; tilting the clamp18 so that the short arm 22, even when raised as shown by the brokenlines in FIG. 4, is adjacent to the floor; elevating the clamp 18 on themast of the truck; and shifting the clamp sideways. Obviously, the clamp18 must be capable of most of these functions if it is to be useful intaking paper rolls out of a boxcar or warehouse space.

Although the invention has been described with particular reference topaper rolls, it is now felt to be apparent that this particular clampmay also be used with other cylindrical loads, and with a suitablechange in pads, with other types of loads.

The present invention, therefore, in well adapted to carry out theobjects and obtain the ends and advantages mentioned, as well as othersinherent therein. While the presently preferred embodiment of theinvention has been given for the purpose of disclosure, numerous changesin the details of construction and the combination, shape, size andarrangement of parts may be resulted to without departing from thespirit and scope of the invention.

What is claimed is:

1. In a clamping attachment for lift trucks and the like:

a frame,

a first load-engaging arm extending from the frame,

a second load-engaging arm extending in the same general direction asthe first arm,

bracket means,

guide means slideably mounting the bracket means on the frame formovement toward and away from the first arm,

the second arm pivotally attached at its inner end to the bracket means,

a toggle linkage pivotally attached to the second arm adjacent the innerend and to the frame, and

actuating means for sliding the bracket means in the guide means,

thereby causing the load-engaging arms to move toward each other in apredetermined path.

2. The invention of claim 1 including:

mounting means holding the first arm,

guide means slideably mounting the mounting means, and

actuating means for sliding the mounting means and first arm toward thesecond arm.

3. A lift truck clamp including:

a frame,

vertically extending guides in the frame,

slides slideably mounted in the guides,

a bracket attached to the slides,

a first load-engaging arm extending from the front of the frame, asecond load-engaging arm pivotally mounted at its inner end on thebracket adjacent the front of the frame, a toggle linkage pivotallyinterconnecting the frame and upper portion of the inner end of thesecond arm, the toggle linkage maintaining the second arm substantiallyperpendicular to thefront of the frame during a first portion of thesliding movement of the bracket, and causing the second arm to pivotabout the bracket during the remaining portion of the sliding movementof the bracket, and means for moving the slides within the guides. 4.The invention of claim 3 wherein the toggle linkage includes:

a crank pivotally attached to the bracket, a rocking lever pivotallyinterconnecting the frame and crank, and a link pivotallyinterconnecting the crank and second arm, the pivotal interconnectionbetween the rocking lever and crank being substantially coincident withthe pivotal mounting of the second arm and bracket during the firstportion of the sliding movement. 5. The invention of claim 3 includingthe first arm being slideably mounted on the frame and means for slidingthe first arm.

1. In a clamping attachment for lift trucks and the like: a frame, afirst load-engaging arm extending from the frame, a second load-engagingarm extending in the same general direction as the first arm, bracketmeans, guide means slideably mounting the bracket means on the frame formovement toward and away from the first arm, the second arm pivotallyattached at its inner end to the bracket means, a toggle linkagepivotally attached to the second arm adjacent the inner end and to theframe, and actuating means for sliding the bracket means in the guidemeans, thereby causing the load-engaging arms to move toward each otherin a predetermined path.
 2. The invention of claim 1 including: mountingmeans holding the first arm, guide means slideably mounting the mountingmeans, and actuating means for sliding the mounting means and first armtoward the second arm.
 3. A lift truck clamp including: a frame,vertically extending guides in the frame, slides slideably mounted inthe guides, a bracket attached to the slides, a first load-engaging armextending from the front of the frame, a second load-engaging armpivotally mounted at its inner end on the bracket adjacent the front ofthe frame, a toggle linkage pivotally interconnecting the frame andupper portion of the inner end of the second arm, the toggle linkagemaintaining the second arm substantially perpendicular to the front ofthe frame during a first portion of the sliding movement of the bracket,and causing the second arm to pivot about the bracket during theremaining portion of the sliding movement of the bracket, and means formoving the slides within the guides.
 4. The invention of claim 3 whereinthe toggle linkage includes: a crank pivotally attached to the bracket,a rocking lever pivotally interconnecting the frame and crank, and alink pivotally interconnecting the crank and second arm, the pivotalinterconnection between the rocking lever and crank being substantiallycoincident with the pivotal mounting of the second arm and bracketduring the first portion of the sliding movement.
 5. The invention ofclaim 3 including the first arm being slideably mounted on the frame andmeans for sliding the first arm.